With an increase in the packing density of LSIs, the required linewidths of circuits included in semiconductor devices become finer year by year. To form a desired circuit pattern on a semiconductor device, a method is employed in which a high-precision original pattern (i.e., a mask, or also particularly called reticle, which is used in a stepper or a scanner) formed on quartz is transferred to a wafer in a reduced manner by using a reduced-projection exposure apparatus. The high-precision original pattern is written by using an electron-beam writing apparatus, in which a so-called electron-beam lithography technique is employed.
Compared with the case of performing writing by using a single electron beam, a writing apparatus using multiple beams may emit many beams at a time, achieving a considerable increase in the throughput. For example, in a multibeam writing apparatus using a blanking aperture array, which is one embodiment of a multibeam writing apparatus, an electron beam emitted from a single electron gun passes through a shaping aperture array having multiple openings. Thus, multiple beams (multiple electron beams) are formed. The multiple beams pass through the respective blankers of the blanking aperture array. The blanking aperture array includes electrode pairs for deflecting the beams individually, and also includes openings through which the beams pass and which are disposed between the respective electrode pairs. The potential of one electrode of an electrode pair (blanker) is fixed to the ground potential, and the potential of the other electrode is switched between the ground potential and a potential different from the ground potential. Thus, blanking deflection is performed on the passing electron beams individually. Electron beams deflected by blankers are blocked, and electron beams which have not been deflected are emitted onto a sample.
In a multibeam writing method, multiple beams are collectively deflected so that writing is performed by using a single electron beam in an area between adjacent electron beams (hereinafter referred to as a subfield). Multiple beams are arranged at equal intervals in a matrix on a sample surface. Therefore, the shape of each of the subfields which corresponds to an area in which the corresponding beam is deflected is square.
The subfields may be rotated due to the positional relationship between the electrodes included in a deflector and an influence of the output characteristics of an amplifier connected to the deflector. Accordingly, the accuracy in a connecting portion between adjacent subfields may be degraded, causing degradation in the pattern writing accuracy. The size of each subfield is small, and it is difficult to obtain an accurate amount of rotation for adjustment.
In a multibeam writing apparatus, when the blanking aperture array having been rotated from a desired position is mounted, the pattern writing accuracy may be degraded. Therefore, it is necessary to obtain the arrangement angle of the blanking aperture array for adjustment of the arrangement angle. Alternatively, it is necessary to adjust, by using lenses, the angle of rotation of a multibeam image.